The present invention is directed to the field of printed circuit board fabrication. More particularly, the present invention is directed to a pattern design (such as a registration coupon mechanism) that allows real time external feature registration assessment.
Electronic systems (e.g., computers, printers, etc.) may be designed with one or more printed circuit boards that are electrically connected together to perform various functions. Manufacturers may follow a well-established circuit board assembly procedure in order to manufacture and assemble a fully functional circuit board. This circuit board assembly procedure may have four sequential stages of which the second, third and fourth stages are performed in an assembly line environment while the first stage is performed beforehand, normally at an off-line site, in an effort to speed up the assembly line stages.
The first stage may involve programming various programmable electronic components using well-known manual or automated equipment operated by one or more persons. These programmable electronic components include, but are not limited to, read-only memory (xe2x80x9cROMxe2x80x9d), erasable programmable read-only memory (xe2x80x9cEPROMxe2x80x9d) and electrically erasable and re-programmable nonvolatile memory (typically referred to as xe2x80x9cflashxe2x80x9d memory). Afterwards, electronic components may be connected to the circuit board during the second or third stages.
The second and third stages may involve assembly of the circuit board by connecting surface mount technology (xe2x80x9cSMTxe2x80x9d) components followed by through hole mount technology (xe2x80x9cTHMTxe2x80x9d) components through various widely known techniques. For example, the technique for connecting SMT components to the circuit board may include the following operations: (i) solder paste application, (ii) proper placement of the SMT components, and (iii) reflow soldering to establish connections between bus lines previously routed in the circuit board and the SMT components. Likewise, the technique for connecting the THMT components may include the following operations: (i) proper placement of THMT components, and (ii) wave soldering.
The final stage in manufacturing circuit boards may involve testing each component (i.e., xe2x80x9cin-circuitxe2x80x9d testing) as well as the entire operation of the circuit board (i.e., xe2x80x9cfunctionalxe2x80x9d testing) to determine whether the circuit board is functioning properly.
It is desirable to notice defects in a printed circuit board (PCB) early in the manufacturing and assembling processes so as to avoid unnecessary assembly. That is, defects may arise from misregistration of holes, vias, pads and/or components. For example, misregistration may occur if drilled holes are not properly registered with outer layer pads or if a solder mask is not properly registered with outer layer pads. If a printed circuit board is defective, then it may be a waste of time and money to mount electronic components on the circuit board since the circuit board may be discarded or returned to the manufacturer due to its defect. It is therefore desirable for an easy and efficient mechanism and method to identify defective printed circuit boards.